In the Evolved Universal Terrestrial Radio Access (E-UTRA) system of the 3rd Generation Partnership Project (3GPP), the shared channel technique is used to improve throughput of a cell and the number of users of the cell.
Downlink data of a cell in the Long Term Evolution (LTE) system is transmitted through the Physical Downlink Shared Channel (PDSCH), and uplink data is transmitted through the Physical Uplink Shared Channel (PUSCH). Scheduling information on the shared channels is sent by the Physical Downlink Control Channel (PUCCH). The Physical Uplink Control Channel (PUCCH) sends uplink control information such as response (ACK/NACK), Channel Quality Indicator (CQI), etc. Downlink Control Information (DCI) transmitted by the PDCCH includes a plurality of formats, wherein some are used for uplink resource scheduling, some are used for downlink resource scheduling, and the others are used for downlink control information of other physical layers, such as power control information, etc. The PDCCH will carry a Radio Network Temporary Identifier (RNTI) in a mask way, including an identifier Cell RNTI (C-RNTI) for denoting control information of a specified User Equipment (UE), an identifier System Information RNTI (SI-RNTI) for denoting control information of cell system information, and an identifier Paging RNTI (P-RNTI) for denoting control information of paging message. Some RNTIs, such as the SI-RNTI and P-RNTI, are used commonly by the UE. When the UE is required to receive a system broadcast message or paging message, particular scheduling information can be obtained by reading PDCCH signaling containing the SI-RNTI or P-RNTI, thereby obtaining the system broadcast message and paging message through the scheduling information. The other RNTIs, such as C-RNTI and Semi-static Persistent Scheduling Radio Network Temporary Identifier (SPS-RNTI), are used specially by the specified UE. A network side will allocate one C-RNTI to a UE after the UE establishes a connection with a network. Afterwards, dynamic resource scheduling information of the UE will be identified by this C-RNTI. The C-RNTI at this time can be used as an identifier of the UE in the cell. The SPS-RNTI is suitable for indicating control information of semi-static persistent scheduling resources of the specified UE. Other Transmit Power Control RNTI (TPC-RNTI), such as Transmit Power Control-Physical Uplink Control Channel-RNTI (TPC-PUCCH-RNTI) and Transmit Power Control-Physical Uplink Shared Channel-RNTI (TPC-PUSCH-RNTI) etc., are identifiers used for indicating power control information of a set of UEs.
The Long Term Evolution-Advanced (LTE-Advanced or LTE-A) system is an evolved version of the LTE. The system will aggregate a plurality of carriers, bandwidths of which satisfy certain requirements, using a way of carrier aggregation so as to support a higher bandwidth and further obtain a higher data rate. FIG. 1 is a schematic diagram of a relationship between carrier aggregation and component carriers in the LTE-A system. As shown in FIG. 1, each aggregated carrier is called as one component carrier, which may be continuous in frequency band or may be discontinuous. Each component carrier is composed of a plurality of sub-carriers, and the number of the sub-carriers contained in each component carrier is determined based on the bandwidth size of the component carrier and frequency interval between the sub-carriers. In addition to satisfying or exceeding all related requirements of “Requirements for Evolved-UTRA (E-UTRA) and Evolved-UTRAN (E-UTRAN)” of 3GPP TR 25.913, the LTE-A system is required to achieve or exceed the requirements of IMT-Advanced proposed by the International Telecommunications Union-Radio communications Sector (ITU-R). The requirement for the LTE Release-8 backward compatibility means that a user equipment of the LTE Release-8 network can work in a LTE-Advanced network; an a user equipment of the LTE-Advanced network can work in a LTE Release-8 network. In addition, the LTE-Advanced network should be able to support aggregation of spectrum with different sizes, and work on spectrum resources (for example continuous spectrum resources of 100 MHz) higher than that of the LTE Release-8 network so as to achieve higher performance and target peak rate. Since the LTE-Advanced network is required to be able to access LTE users, its working frequency band is required to cover the frequency band of the current LTE, on which the available continuous spectrum bandwidth of 100 MHz has not existed. Therefore, a direct problem required to be solved by the LTE-Advanced network is to aggregate a plurality of component carriers having one of six LTE working bandwidths distributed in different bands to form wide bandwidth resources which can be used by the LTE-Advanced network. Considering the compatibility with the LTE Release-8 network, each component carrier of the LTE-Advanced network is required to satisfy the requirement that LTE users can be accessed. These carriers are called as backward compatible carriers, and like the common LTE for a UE of the LTE. Thus one cell of the LTE-A may be composed of a plurality of backward compatible carriers. For a terminal of the LTE, each backward compatible carrier may be considered as one LTE cell, and for the terminal of the LTE-A, the carrier aggregation can be carried out using a plurality of carriers. Non backward compatible carriers, which are unable to be used by the terminal of the LTE but can be used as carrier aggregation by the terminal of the LTE-A, are different from backward compatible carriers. In a LTE-A cell, since the LTE-A extends the working bandwidth of the UE from the maximal of 20 MHz of the LTE to the maximal of 100 MHz of the LTE-A, the 100 MHz of the LTE-A may be continuous in frequency band or may be discontinuous, and even may support discontinuous carrier aggregation across frequency bands, that is to say, the discontinuous carriers are located in different frequency bands respectively, for example, one carrier is at 1.8 GHz, and another carrier is at 2.6 GHz, resulting in the UE of the LTE-A being required to aggregate two component carriers with a very large frequency span, which puts forward a very high requirement for radio frequency and base band processing capabilities of the UE.
The LTE-A technique is required to, on the one hand, keep the compatibility with the LTE, on the other hand, decrease the complexity of the LTE-A terminal, because the UE of the LTE-A is required to not only work in the LTE cell, but also support carrier aggregation. Unlike the LTE-A system, there is the only one carrier in the LTE cell, thus when the UE of the LTE works in the LTE cell or the backward compatible carriers of the LTE-A, there is no carrier selection problem. However, when the UE of the LTE-A works in the LTE-A cell, and when the LTE-A cell is composed of a plurality of component carriers, how the UE of the LTE-A uses physical resources under a plurality of carriers becomes a problem to be solved urgently.